Various designs of such hemming devices have been known from practice. They have a hemming head, which has one hemming tool or a plurality of hemming tools divided into segments. The hemming tool or hemming tools is/are provided with a hemming edge rotating in the operating position. The hemming device also has a stroke drive for generating the hemming stroke and an adjusting means for retracting and extending the segments. Such hemming devices are intended mainly for workpieces with an internal opening, e.g., vehicle doors with a window opening. In the retracted resting position of the segments, the hemming head can move up and down in the opening of the workpiece. In the extended operating position, the segments bead the sheet metal edges. The prior-art hemming devices have an adjusting means, which operates in one step or two steps and moves the segments in two or more groups one after the other. This requires a plurality of drives and implies a more complicated control and design. In addition, this technique is to the detriment of the cycle time.